MSG Health Impacts and Sensitivity

Glutamate. Its applications in food and contribution to health.
S.Jinap and P. Hajeb
Appetite (2010), doi: 10.1016/j.appet.2010.05.002

This article reviews the application of glutamate in food and its benefits and role as one of the common food ingredients used. Monosodium glutamate is one of the most abundant naturally occurring amino acids which is frequently added as a flavour enhancer. It produces a unique taste, that cannot be provided by other basic tastes (saltiness, sourness, sweetness and bitterness), referred to as a fifth taste (umami). Glutamate serves some functions in the body as well, serving as an energy source for certain tissues and as a substrate for glutathione synthesis. Glutamate has the potential to enhance food intake in older individuals and dietary free glutamate evokes a visceral sensation from the stomach, intestine and portal vein. Small quantities of glutamate used in combination with a reduced amount of table salt during food preparation allow for far less salt to be used during and after cooking. Because glutamate is one of the most intensely studied food ingredients in the food supply and has been found safe, the Joint Expert Committee on Food Additives of the United Nations Food and Agriculture Organization and World Health Organization placed it in the safest category for food additives. Despite a widespread belief that glutamate can elicit asthma, migraine headache and Chinese Restaurant Syndrome (CRS), there are no consistent clinical data to support this claim. In addition, findings from the literature indicate that there is no consistent evidence to suggest that individuals may be uniquely sensitive to glutamate.

Introduction and Summary of the 2018 Dietary Glutamate Workshop
Cynober L., Fernstrom J.D., Koletzko B., Rietjens I.M.C.M., Roberts A., Tennant D.R., Tomé D., Vorhees C.V.
Ann Nutr Metab (2018), doi: 10.1016/j.appet.2010.05.002

Conclusion: “The current estimated dietary exposure to glutamates resulting from use as food additives (E620–E625) at both the mean and the 95th percentile remains far below this suggested value of at least 240 mg/kg body weight per day. Considering the metabolic pathways of glutamate, the self-limiting character of glutamate taste (umami), and the fact that a practical limit on glutamate use in final foods already exists (10 g/kg of food), there are no compelling arguments to warrant change of the ADI of “not specified.” This fact has been already recognized by the other respected regulatory bodies, including the US Food and Drug Administration and the Food Standards Australia New Zealand.”

Monosodium glutamate is not associated with obesity or a greater prevalence of weight gain over 5 years: findings from the Jiangsu Nutrition Study of Chinese adults.
Shi Z, Luscombe-Marsh ND, Wittert GA, Yuan B, Dai Y, Pan X, Taylor AW.
Br J Nutr. 2010 Apr 7:1-7.

Animal studies and one large cross-sectional study of 752 healthy Chinese men and women suggest that monosodium glutamate (MSG) may be associated with overweight/obesity, and these findings raise public concern over the use of MSG as a flavour enhancer in many commercial foods. The aim of this analysis was to investigate a possible association between MSG intake and obesity, and determine whether a greater MSG intake is associated with a clinically significant weight gain over 5 years. Data from 1282 Chinese men and women who participated in the Jiangsu Nutrition Study were analysed. In the present study, MSG intake and body weight were quantitatively assessed in 2002 and followed up in 2007. MSG intake was not associated with significant weight gain after adjusting for age, sex, multiple lifestyle factors and energy intake. When total glutamate intake was added to the model, an inverse association between MSG intake and 5 % weight gain was found (P = 0.028), but when the model was adjusted for either rice intake or food patterns, this association was abolished. These findings indicate that when other food items or dietary patterns are accounted for, no association exists between MSG intake and weight gain.

Glutamic Acid, the Main Dietary Amino Acid, and Blood Pressure. The INTERMAP Study (International Collaborative Study of Macronutrients, Micronutrients and Blood Pressure)
Jeremiah Stamler MD*, Ian J. Brown PhD, Martha L. Daviglus MD, PhD, Queenie Chan MPhil, Hugo Kesteloot MD, PhD, Hirotsugu Ueshima MD, PhD, Liancheng Zhao MD, Paul Elliott MB, PhD, for the INTERMAP Research Group
Circulation.2009 (Published online before print July 6, 2009)

Background: Data are available that indicate an independent inverse relationship of dietary vegetable protein to the blood pressure (BP) of individuals. Here, we assess whether BP is associated with glutamic acid intake (the predominant dietary amino acid, especially in vegetable protein) and with each of 4 other amino acids that are relatively higher in vegetable than animal protein (proline, phenylalanine, serine, and cystine). METHODS AND RESULTS: This was a cross-sectional epidemiological study with 4680 persons 40 to 59 years of age from 17 random population samples in China, Japan, the United Kingdom, and the United States. BP was measured 8 times at 4 visits; dietary data (83 nutrients, 18 amino acids) were obtained from 4 standardized, multipass, 24-hour dietary recalls and 2 timed 24-hour urine collections. Dietary glutamic acid (percentage of total protein intake) was inversely related to BP. Across multivariate regression models (model 1, which controlled for age, gender, and sample, through model 5, which controlled for 16 possible nonnutrient and nutrient confounders), estimated average BP differences associated with a glutamic acid intake that was higher by 4.72% of total dietary protein (2 SD) were -1.5 to -3.0 mm Hg systolic and -1.0 to -1.6 mm Hg diastolic (z scores -2.15 to -5.11). Results were similar for the glutamic acid-BP relationship with each of the other amino acids also in the model; eg, with control for 15 variables plus proline, systolic/diastolic pressure differences were -2.7/-2.0 mm Hg (z scores -2.51, -2.82). In these 2-amino acid models, higher intake (by 2 SD) of each of the other amino acids was associated with small BP differences and z scores. CONCLUSIONS: Dietary glutamic acid may have independent BP-lowering effects, which may contribute to the inverse relation of vegetable protein to BP.

Monosodium glutamate ‘allergy’: menace or myth?
A.N. Williams and K. M. Woessner
Clinical & Experimental Allergy, 39, 640-646

Monosodium glutamate (MSG) is a salt form of a non-essential amino acid commonly used as a food additive for its unique flavour enhancing qualities. Since the first description of the ‘monosodium glutamate symptom complex’, originally described in 1968 as the ‘Chinese restaurant syndrome’, a number of anecdotal reports and small clinical studies of variable quality have attributed a variety of symptoms to the dietary ingestion of MSG. Descriptions of MSG-induced asthma, urticaria, angio-oedema, and rhinitis have prompted some to suggest that MSG should be an aetiologic consideration in patients presenting with these conditions. This review presents a critical review of the available literature related to the possible role of MSG in the so-called ‘Chinese restaurant syndrome’ and in eliciting asthmatic bronchospasm, urticaria, angio-oedema, and rhinitis. Despite concerns raised by early reports, decades of research have failed to demonstrate a clear and consistent relationship between MSG ingestion and the development of these conditions.

Supplement The Safety Evaluation of Monosodium Glutamate
Ronald Walker and John R. Lupien*
Journal of Nutrition. 2000;130:1049S-1052S. School of Biological Sciences, University of Surrey, Guildford GU2 5XH, Surrey, UK and *Food and Nutrition Division, FAO, 00100 Roma, Italy

L-Glutamic acid and its ammonium, calcium, monosodium and potassium salts were evaluated by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) in 1988. The Committee noted that intestinal and hepatic metabolism results in elevation of levels in systemic circulation only after extremely high doses given by gavage (>30mg/kg body weight). Ingestion of monosodium glutamate (MSG) was not associated with elevated levels in maternal milk, and glutamate did not readily pass the placental barrier. Human infants metabolized glutamate similarly to adults. Conventional toxicity studies using dietary administration of MSG in several species did not reveal any specific toxic or carcinogenic effects nor were there any adverse outcomes in reproduction and teratology studies. Attention was paid to central nervous system lesions produced in several species after parenteral administration of MSG or as a consequence of very high doses by gavage. Comparative studies indicated that the neonatal mouse was most sensitive to neuronal injury; older animals and other species (including primates) were less so. Blood levels of glutamate associated with lesions of the hypothalamus in the neonatal mouse were not approached in humans even after bolus doses of 10 g MSG in drinking water. Because human studies failed to confirm an involvement of MSG in “Chinese Restaurant Syndrome” or other idiosyncratic intolerance, the JECFA allocated an “acceptable daily intake (ADI) not specified” to glutamic acid and its salts. No additional risk to infants was indicated. The Scientific Committee for Food (SCF) of the European Commission reached a similar evaluation in 1991. The conclusions of a subsequent review by the Federation of American Societies for Experimental Biology (FASEB) and the Federal Drug Administration (FDA) did not discount the existence of a sensitive subpopulation but otherwise concurred with the safety evaluation of JECFA and the SCF.